The following discussion of the background to the invention is intended to facilitate an understanding of the invention. However, it should be appreciated that the discussion is not an acknowledgement or admission that any of the material referred to was published, known or part of the common general knowledge as at the priority date of the application.
High performance composite components can be limited in their application due to softening of the polymer matrix in the composite material when exposed to high levels of thermal energy. In this regard, applications which cause a composite component to be heated outside of its service temperature can result in reduced mechanical performance of the component when placed under mechanical load. One such example application in which an external heat source is applied to a composite component is that of a composite automotive component, for example a wheel, being exposed to the radiant or convective thermal energy from an adjacent brake calliper and rotor assembly during the braking process.
For this reason it is generally necessary to shield composite components from external heat sources (whether radiant, conductive or convective) which could raise the temperature of the composite component above the glass transition temperature Tg at which the integrity and/or performance of the matrix material within the composite can become compromised.
Previous attempts to address this issue have included the development of higher Tg resins providing a composite matrix with greater heat resistance. However this approach increases overall composite cost and, moreover, there are many applications for which there is no suitable resin having the required service temperature.
Alternative previous systems have utilised a metallic heat shield spaced apart from the composite surface to provide an air gap or buffer between the heat source and the composite surface. However it will be appreciated that this solution is cumbersome and undesirably necessitates additional space to be provided surrounding the composite component.
In other prior systems, metallic or ceramic protective coatings have been adhesively bonded to the composite surfaces, some coatings being integrally formed with grid structures to limit contact with the composite surface thereby reducing the thermal conductivity between the protective coating and the composite surface. In yet another system, a number of protective coatings is applied to the composite surface by means of thermal spraying. These thermal protection systems rely on the adhesion between the protective coating/shield and to the composite surface. However the interface between the carbon fibre composite surface and the various prior bonding coats (generally metallic) has traditionally provided for poor chemical and mechanical bonding. As such, the delamination of thermal protection coatings is a persistent issue in the field of composite materials including for the above-noted prior systems.
It is therefore desirable to provide an alternative and/or improved method of producing a thermally protected composite component.